Soak the whole thing , total immersion, for an hour or two - put a big spoonful of sugar in the warm water. Then it will come out of the pot easily, and you will have given it a flying start for its growth after your potting operation.
But, no plant lives for ever, maybe its time has come - so to sound a different note - these hybrid phallies are so cheap these days, that I would wonder whether the whole operation was worth it. Why not go out and buy a new plant, in the peak of health, already flowering ?